English

Metric freedom and projectivity for classical and quantum normed modules

Functional Analysis 2011-12-30 v1

Abstract

In functional analysis there are several reasonable approaches to the notion of a projective module. We show that a certain general-categorical framework contains, as particular cases, all known versions. In this scheme, the notion of a free object comes to the forefront, and in the best of categories, called freedom-loving, all projective objects are exactly retracts of free objects. We concentrate on the so-called metric version of projectivity and characterize metrically free `classical', as well as quantum (= operator) normed modules. Hitherto known the so-called extreme projectivity turns out to be, speaking informally, a kind of `asymptotically metric projectivity'. Besides, we answer the following concrete question: what can be said about metrically projective modules in the simplest case of normed spaces? We prove that metrically projective normed spaces are exactly l10(M)l_1^0(M), the subspaces of l1(M)l_1(M), where MM is a set, consisting of finitely supported functions. Thus in this case the projectivity coincides with the freedom.

Keywords

Cite

@article{arxiv.1112.5750,
  title  = {Metric freedom and projectivity for classical and quantum normed modules},
  author = {A. Ya. Helemskii},
  journal= {arXiv preprint arXiv:1112.5750},
  year   = {2011}
}

Comments

27 pages

R2 v1 2026-06-21T19:56:45.762Z